1. Field of the Invention
The present invention relates to a disposable diaper of an underpants type or an open type and, more particularly, to a disposable diaper which enables securely holding of an absorbent core by a top sheet.
2. Description of the Related Art
FIG. 10 is a sectional view of such a portion of the underpants or open type diaper of the related art as to be applied to a crotch.
As shown in FIG. 10, a disposable diaper 100 of this kind includes: a liquid-permeable top sheet 101 to be directed to the side of a wearer (or a liquid receiving side); and a liquid-impermeable outer sheet 102 to be directed outward. The top sheet 101 and the outer sheet 102 are bonded to each other at two transverse side regions 100a and 100a of the diaper. In a transverse center region 100b, on the other hand, there is sandwiched between the aforementioned top sheet 101 and outer sheet 102 an absorbent core 103 which is made mainly of a fibrous material such as pulp and contains a highly absorbent resin.
In a process of the related art for manufacturing the disposable diaper of this kind, the absorbent core 103 is placed on the outer sheet 102 developed in a planar shape and is then overlaid by the top sheet 101 which is also developed in a planar shape. At this time, in the related art, the adhesion of the top sheet 101 is limited such that the top sheet 101 is adhered to the outer sheet 102 in the aforementioned two side regions 100a and 100a and to an upper surface 103a of the absorbent core 103 in a rising upper face 100c on the liquid receiving side.
In the related art, more specifically, the top sheet 101 is adhered only by pressing it vertically. As a result, the top sheet 101 is adhered only at the horizontal face such as the aforementioned two side regions 100a or rising upper face 100c but not at the non-horizontal face such as two side ends 103c of the absorbent core 103.
Thus, the two side ends 103c of the absorbent core 103 and the top sheet 101 are not adhered, but the absorbent core 103 has a thickness. As a result, spaces 104 and 104 are easily formed between the two side ends 103c and 103c of the absorbent core 103 and the top sheet 101.
In the disposable diaper of the related art, as shown in FIG. 10, the two side ends 103c and 103c of the absorbent core 103 and the top sheet 101 are not adhered, but the spaces 104 and 104 are formed between the two side ends 103c and 103c and the top sheet 101. As a result, the absorbent core 103 is insufficiently held by the top sheet 101. The holding force of the absorbent core 103 is weakened especially in the transverse direction, i.e., leftward or rightward of FIG. 10.
If the wearer moves while wearing the disposable diaper, a twisting force, a transverse offsetting force and a kinking force act on the absorbent core 103. Especially for the underpants type diaper, the wearer walks or crawls while wearing the disposable diaper so that the aforementioned forces to be applied to the aforementioned absorbent core 103 increase.
If the aforementioned forces continuously act, the absorbent core 103 will be twisted or offset at the aforementioned center region 100b of the diaper. As a result, the spaces 104 and 104 between the two side ends 103c and 103c of the absorbent core 103 and the top sheet 101 will easily spread. If the absorbent core 103 is kinked leftward or rightward, moreover, the upper surface 103a of the absorbent core 103 wrinkles to separate the adhesion between the upper surface 103a of the absorbent core 103 and the top sheet 101, thereby to cause a clearance between the upper surface 103a and the top sheet 101.
If the spaces 104 spread or if the clearance is caused between the upper surface 103a and the top sheet 101, as described above, the liquid such as urine fed to the top sheet 101 cannot be efficiently absorbed by the absorbent core 103 to cause the transverse leakage of urine in the diaper.
The invention has an object to provide a disposable diaper which is hardly experienced by a twist, offset or kink of an absorbent core in the diaper by stabilizing the holding, i.e., the transverse holding of the absorbent core by a top sheet, so that the absorbing function of the absorbent core can be prevented from any reduction.
According to a first aspect of the invention, there is provided a disposable diaper having a body including a front face portion to be applied to the abdomen of a wearer; an intermediate portion to be applied to the crotch; and a back face portion to be applied to the back, in which a longitudinal direction is taken from the front face portion to the back face portion of the body, and a transverse direction is taken in a direction perpendicular to the longitudinal direction, which comprises a top sheet to be directed toward a liquid receiving side; an outer sheet; and an absorbent core sandwiched between the top sheet and the outer sheet, the top sheet being liquid-permeable at least in a portion for covering a transverse center of the absorbent core and being jointed on two transverse sides directly or indirectly to the outer sheet, wherein, in a region containing at least a longitudinal center of the intermediate portion, joint boundaries between the top sheet and the outer sheet enter farther the transverse center side than two transverse side ends of the absorbent core.
Here, the aforementioned top sheet and outer sheet may be adhered and jointed directly to each other or through another sheet. On the other hand, the top sheet may be made liquid-permeable in its portion covering at least the absorbent core.
In the diaper according to the first aspect of the invention, the top sheet is in contact with not only the liquid receiving side surface of the absorbent core but also the two transverse side ends of the absorbent core, and enters the two end portions of the back side of the absorbent core. As a result, the absorbent core can be wrapped and restricted from the two transverse sides by the top sheet so that the absorbent core is hardly twisted, offset and kinked.
Here, the top sheet may include a liquid-permeable sheet and side sheets directly or indirectly jointed to the liquid-permeable sheet on two transverse sides thereof, and joint boundaries between the side sheets and the outer sheet may enter farther the transverse center side than the two transverse side ends of the absorbent core.
Here, it is preferable that in the region containing at least the longitudinal center of the intermediate portion, the top sheet is jointed to the two transverse side ends of the absorbent core.
On the other hand, the liquid receiving side surface of the absorbent core and the top sheet are usually adhered to each other. When the back side of the absorbent core and the outer sheet are adhered, moreover, the absorbent core can be reliably held on the diaper.
In the diaper according to the first aspect of the invention, the aforementioned top sheet and the outer sheet may be jointed at the two transverse sides after the top sheet was so pressed or shaped as to wrap the absorbent core from the upper surface to the two side ends thereof.
However, if in the region containing at least the longitudinal center of the intermediate portion, there is disposed elasticity applying means for bringing the joint boundaries closer to the transverse center, it is easy to form a structure in which the two side ends of the absorbent core are wrapped by the top sheet.
In this case, it is preferable that the top sheet is not elastically shrunken in the transverse direction, or that the transverse elastic shrinking distortion in the free state of the diaper is made larger at the elasticity applying means than at the top sheet.
By combining such top sheet with the elasticity applying means, the shrinking force of the aforementioned elasticity applying means can be utilized to easily realize a structure in which the two side ends of the absorbent core are wrapped by the top sheet.
According to a second aspect of the invention, on the other hand, there is provided a disposable diaper having a body including a front face portion to be applied to the abdomen of a wearer; an intermediate portion to be applied to the crotch; and a back face portion to be applied to the back, in which a longitudinal direction is taken from the front face portion to the back face portion of the body, and a transverse direction is taken in a direction perpendicular to the longitudinal direction, which comprises a top sheet to be directed toward a liquid receiving side; an outer sheet; and an absorbent core sandwiched between the top sheet and the outer sheet, the top sheet being liquid-permeable at least in a portion for covering a transverse center of the absorbent core and being jointed on two transverse sides directly or indirectly to the outer sheet, wherein, in a region containing at least a longitudinal center of the intermediate portion, there is disposed elasticity applying means for bringing joint boundaries between the top sheet and the outer sheet closer to the transverse center; wherein the top sheet is not elastically shrunken in the transverse direction, or the transverse elastic shrinking distortion in the free state of the diaper is made larger at the elasticity applying means than at the top sheet; and wherein, in the region containing at least the longitudinal center of the intermediate portion, the top sheet is jointed to two transverse side ends of the absorbent core.
Here, the top sheet may include a liquid-permeable sheet and side sheets directly or indirectly jointed to the liquid-permeable sheet on two transverse sides thereof; the liquid permeable sheet or the side sheets may be not elastically shrunken in the transverse direction, or the transverse elastic shrinking distortion in the free state of the diaper may be made larger at the elasticity applying means than at the liquid-permeable sheet or the side sheets; and in the region containing at least the longitudinal center of the intermediate portion, the liquid-permeable sheet or the side sheets may be jointed to the two transverse side ends of the absorbent core.
The diaper according to the second aspect of the invention is on the premise that there is provided the elasticity applying means for bringing the joint boundaries between the top sheet and the outer sheet to the transverse center, and the aforementioned two transverse side ends of the absorbent core and the aforementioned top sheet are jointed.
By using the elasticity applying means, in the diaper according to the second aspect of the invention, the two side ends of the absorbent core can be reliably wrapped by the top sheet. Since the two side ends of the absorbent core and the top sheet are jointed to each other, moreover, the kink of the absorbent core in the diaper or the like is hardly caused.
In the aforementioned structure, the outer sheet may be an elastically shrinking sheet for elastically shrinking in the transverse direction, for example a shrinking nonwoven fabric or shrinking film, etc. and the elastic shrinking force of the outer sheet may be used as the elasticity applying means.
Alternatively, the elasticity applying means may be an elastic member such as a plurality of elastic bands for exhibiting an elastic shrinking force in the transverse direction, and the elastic member may be fixed in a transversely extended state either between the absorbent core and the outer sheet or on the outer face of the outer sheet.
In the diaper according to the first or second aspect of the invention, moreover, it is preferable: that leakage-preventing cuffs are arranged on the liquid receiving side of the body and are extended in the longitudinal direction and spaced apart from each other in the transverse direction, that the leakage-preventing cuffs include: sheets having fixed end portions fixed on the diaper along the longitudinal direction and free end portions; and elastic members attached to the sheets at the free end portions or at their vicinities for exhibiting shrinking forces in the longitudinal direction, and that in the region containing at least the longitudinal center of the intermediate portion, the fixed end portions of the leakage-preventing cuffs are apart from the two transverse side ends of the absorbent core so that the liquid can be absorbed at the two side ends by the absorbent core.
On the other hand, leakage-preventing cuffs may be arranged on the liquid receiving side of the body and may be extended in the longitudinal direction and spaced apart from each other in the transverse direction, the leakage-preventing cuffs may include: sheets having fixed end portions fixed on the body along the longitudinal direction and free end portions; and elastic members attached to the sheets at the free end portions or at their vicinities for exhibiting shrinking forces in the longitudinal direction, and the sheets for forming the leakage-preventing cuffs may be used as the side sheets. The joint boundaries between the side sheets and the outer sheet may enter farther the center side than the two transverse side ends of the absorbent core, or the aforementioned side sheets may be jointed to the two transverse side ends of the absorbent core.
Moreover, the invention is effective for the structure, in which two transverse side portions of the front face portion and two transverse side portions of the back face portion are jointed to each other, in which a waist opening is formed from individual edge portions of the front face portion and the back face portion, and in which leg openings are formed from two side portions of the intermediate portion so that the body has an underpants shape. However, the invention could also be applied to the open type diaper.